This proposal is in response to an RFP for Extramural Assessment Teams and comes from the American Academy of Orthopaedic Surgeons which represents over 90% of orthopedic surgeons in the U.S.A. A multidisciplinary team assessment of total hip arthroplasty is (THA) proposed. An analysis of small area variation in THA will be done using Medicare A and B files to identify areas of high and low utilization. These areas will be studied in detail by recruiting orthopedic surgeons, rheumatologists, and their patients who have hip pain with significant cartilage loss. A decision analytical Markov model will be developed on treating endstage hip disease by total hip arthroplasty versus alternative treatments. Utilities will be derived from a quantitative synthesis of the literature and, when it is not available, by a consensus of experts. Patient utilities and preferences will be obtained from the study of the patients who have elected total hip arthroplasty or who are receiving conservative management. The results of total hip arthroplasty in the study areas will be fed back to physicians and patients in an effort to reduce utilization of total hip arthroplasty which results in adverse outcomes or inappropriate utilization.